Bronzing principle and process overview

With the improvement of the national economy and the development of the printing and packaging industry, people require the packaging of products: high-end, exquisite, environmentally friendly, and personalized. In the post-press processing of packaging products, the hot stamping process is loved by people because of its unique surface finishing effect, and is used in high-end packaging such as banknotes, cigarette labels, medicines, cosmetics and so on. Bronzing has two main functions. One is surface decoration, which increases the added value of the product. The hobby of festiveness and splendor of gold is the national tradition of China. The combination of bronzing and embossing process to show its luxury; the second is to give the product high anti-counterfeiting performance, the use of holographic positioning hot stamping trademark logo, anti-counterfeiting, brand name protection. At the same time, bronzing can express the personalization of product packaging and is safe and environmentally friendly. Therefore, many high-end packaging uses the bronzing process.

1. Bronzing principle: After a certain temperature and pressure, the colored foil instantly attaches the pattern and text of the plate to the plastic surface.

2. The necessary conditions for hot stamping: 1, temperature 2, air pressure 3, color foil 4, hot stamping version

3. Bronzing version:

High-quality bronzing version is the primary factor to ensure the quality of bronzing. At present, the photo-etching process and electronic engraving technology are mainly used for making bronzing plates, and the materials are usually copper plate or zinc plate. The copper plate material is exquisite, and the surface finish and heat transfer effect are better than the zinc plate. The use of high-quality copper plate can improve the gloss and outline clarity of bronzing graphics. The traditional photo-etching technique for making bronzing plates is simple and low-cost. It is mainly used for text, thick lines, and general images. For finer, uneven graphics and other bronzing plates, secondary roasting or electric engraving technology is required. The bronzing version produced by electro-engraving can express rich and delicate level changes, which greatly expands the packaging performance. This process is beneficial to environmental protection, but the investment in electro-engraving equipment is large. At present, the depth of engraving is not ideal, and it is easy to cause bronzing "pasting. The production technology of holographic anti-counterfeiting bronzing plate is relatively high. Previously it was mainly made in Taiwan or abroad. The plate-making period was longer. It was only used for packaging of fixed and large-volume products.

At present, there are several units in Yuncheng, Shanxi, Beijing and Shanghai. The bronzing version is mainly made of the following materials:

(1). Silicone plate (rubber wheel): suitable for general plastic shell, thickness is generally 1.5MM, suitable temperature is 180 â„ƒ -380 â„ƒ
(2). Copperplate: It is suitable for a large amount of deep bronzing and is durable. Temperature 120 â„ƒ -180 â„ƒ
(3). Zinc plate: Not resistant to high temperature and high pressure, applicable temperature is 120 â„ƒ -150 â„ƒ
(4). Steel version: unused (5). Magnesium alloy version: unused

4. Color foil:

(1) Thickness of color foil: The thickness of the color foil is 6U-35U. The factory generally uses 12U color with less ironing. The color foil is thicker and the font is thicker and clearer.

(2) The color foil is divided into five layers: PE film, release agent, color coating layer, adhesive, and adhesive

(3) Classification of colored foil:
a. General type: generally used for ABS, PVC, PS, PC
b. Special type (PP color foil): generally used for PP, PE
c. Common type: suitable for ABS and PP (this foil has good temperature resistance)

With the rapid development of hot stamping foil and packaging industry, the application of anodized aluminum bronzing is becoming more and more extensive. Such as: book cover hot stamping, gift box hot stamping, tobacco, wine, clothing trademarks and box hot stamping, greeting cards, invitations, pen hot stamping, etc., its many colors and patterns, can also be customized according to specific requirements special edition. The base materials for hot stamping include general paper, gold, silver ink and other ink printing paper, plastic (PK, PP, PVC, engineering plastics such as ABS, etc.), leather, wood and other special materials.

Anodized aluminum hot stamping foil mainly uses heat and pressure to transfer the pattern or text to the surface of the hot stamping material. To complete this process, you need a hot stamping machine, a template with special text or patterns (such as zinc plate, copper plate, etc.), heated to the required temperature, transfer the required pressure and maintain the corresponding elbow. It should be noted that when stamping different materials, the appropriate model of anodized aluminum should be selected, and the appropriate temperature, pressure, and stamping time should be selected to achieve the desired stamping effect.

5. Hot stamping equipment:

The hot stamping workshop currently has six stations, eight stations, flat ironing machine, round ironing machine, special-shaped machine, hot stamping machine, double round machine

Six-station machine: various round faces, irregular whole faces, lines, transfers, etc.
Eight-station machine: the entire surface of various round faces, line decoration and transfer.
Ironing machine: used for ironing flat products.
Round ironing machine: used for ironing round fonts and side lines, etc.
Special-shaped machine: the whole surface and line hot decoration of various irregular products.
Hot stamping machine: used for hot decoration of various flat products.
Double round machine: used for round products.

The selection of bronzing equipment is a key factor in determining the quality of bronzing. The sheet-foil stamping machine has three types: flattening, round flattening, and round flattening. At present, the largest application is the flattening type, mainly including: Shanghai Yahua Printing Machinery Co., Ltd. TYM series die-cutting bronzing two By machine, the TYMl020 automatic bronzing die-cutting machine of Tangshan Yuyin Group Co., Ltd. and MK series automatic bronzing die-cutting machine of Tianjin Youheng Machinery Industry Co., Ltd., the maximum bronzing speed is 5000 sheets / hour. The STOER FOLLJETFBRl04 hot stamping machine is the representative of round pressing. Using the design concept of the offset press, the maximum hot stamping speed can reach 10,000 sheets / hour, and it is currently the fastest single stamping equipment in the world. The three stamping methods of round flattening, round flattening and flat flattening each have their own advantages and disadvantages: the implementation of round flattening and round flattening hot stamping is linear pressure, the total pressure is small, and it is easily completed with a relatively small pressure Large-area hot stamping on the ground, smooth movement, and high production efficiency of the round pressing round type, especially suitable for hot stamping of large batches of live parts, but because the copper plate arc surface processing is more difficult, the production cost is higher, and the heating roller is also more difficult to heat than the plane. Flat and flat operation is flexible and convenient, and is more suitable for short version products. Compared with imported hot stamping equipment, the domestic hot stamping equipment has obvious advantages in performance and price. The price of the domestic machine is only equivalent to l / 5 ~ 1/4 of the price of similar foreign products, but the accuracy, stability, and function of the overprint of the imported machine are all It is obviously superior to domestic machines, and is more durable than domestic machines. It is more suitable for processing fixed batches of high-end packaging products. Therefore, product type and batch size are the key to determine the selection of bronzing equipment. Whether it has high-end bronzing die-cutting equipment such as BOBST has become the first choice for customers in the industry.

6. Features of bronzing:

The pattern is clear, beautiful, colorful and eye-catching, wear-resistant and weather-resistant. On the printed cigarette labels, the application of bronzing technology accounts for more than 85%. And bronzing in graphic design can play a finishing touch and highlight the design theme, especially for trademarks and registered names, the effect is more remarkable.

7. Application of the product:

(1). Common gold and laser gold hot stamping. It can be used for hot stamping on most products, including gold cards, silver cards, laser cards and glass cards, and its application is more common.

(2). Location holographic bronzing. Holographic laser positioning anodized aluminum is a special process application in design, with corresponding anti-counterfeiting patterns, which can greatly improve the anti-counterfeiting ability of the product, and can also improve the product grade. This kind of anodized aluminum is generally produced domestically, compared with foreign imports, the price is cheaper, but the bronzing performance is slightly worse. Holographic laser positioning anodized aluminum controls the bronzing temperature, bronzing pressure and vehicle speed, and even the bronzing models have a great relationship.

(3). Special application of anodized aluminum in the process. Hot after printing is a new idea in cigarette label design and printing industry. The application of this process has high requirements for anodized aluminum. In addition to achieving accurate bronzing position, smooth and bright surface, balanced and uniform pressure, no foam, no paste, etc., special attention must be paid to the edge of the bronzing pattern. Marks, gold foil anodized aluminum should have good adhesion on the stamping surface, and no obvious scratches and scratches. Everyone knows that the bronzing process is actually a process in which the paper is heated and compressed. For white cards and glass cards, special attention should be paid to the protection of semi-finished products. In the production process, various unfavorable factors of paper deformation should be minimized. This will greatly help the smooth progress of the post-gilding process and the improvement of product qualification rate.

8. Hot stamping and its quality control

The so-called bronzing suitability refers to the selection of anodized aluminum models and the matching between bronzing speed, temperature, pressure and other factors. When the hardware such as equipment is fixed, correctly grasping the suitability of bronzing is the most important means to improve the quality of bronzing. The following is an analysis of some quality problems reflected from the actual operation, in order to scientifically grasp the suitability of bronzing.

1. Hot stamping does not work or is not true

This is related to various factors such as the surface characteristics of the printed parts, the properties of the anodized aluminum, the hot stamping temperature and the pressure. â‘ Too much powder is sprayed on the surface of the printing piece or the surface contains additives such as debonding agent and gloss paste, which will hinder the adsorption of the anodized aluminum and the paper. Solution: Surface powder removal treatment or solution in the printing process. â‘¡ Improper selection of anodized aluminum directly affects the fastness of bronzing. The type of anodized aluminum used should be comprehensively considered according to the size of the gold foil area and the characteristics of the material to be stamped. The domestic anodized aluminum is mainly the Peacock brand series produced by Shanghai Shenyong Bronzing Material Co., Ltd., and the imported anodized aluminum is mainly the PM and LK series of KURZ in Germany, the A, K, and H series in Japan, and the SP series of KOLON in South Korea. . According to our practice and testing, the selection of anodized aluminum can mainly refer to the following categories: hot stamping on general products (general ink color), anodized aluminum has 88-1 type, KURZ PM type; dense ink color printed products such as cigarette packs, cosmetics (including printed Gold, printed silver) hot stamping anodized aluminum has 88-2 type; cigarette marks, cosmetic packaging and other fine handwriting hot stamping anodized aluminum has 88-3, 88-4 type, PM288, etc .; suitable for OPP or PET laminated paper There are 88-4 type, K series, LK series, and SP series for the hot stamping of anodized aluminum with UV ink on cardboard, glazing paper and other products. â‘§ Failure to properly grasp the stamping equipment and the matching between the stamping time and the stamping temperature, which affects the stamping fastness and the clarity of the graphic outline. Due to the different equipment and materials to be stamped, the stamping time and stamping temperature are different. For example, the high-speed circular rounding machine is fast and the stamping line contacts, and the hot stamping temperature is higher than the circular flattening or flattening. In general, the temperature of round pressing and round hot stamping is 190 â„ƒ ï½ž 220 â„ƒ, the round pressing is about 130 â„ƒ ï½ž 150 â„ƒ, and the flat pressing is about 100 â„ƒ ï½ž 120 â„ƒ. Of course, the pressing time, hot stamping temperature and production efficiency are also largely restricted by the transfer performance of anodized aluminum.

2. Pull back

Reverse pulling means that the anodized aluminum will remove the printing ink or the varnish of the printed parts after hot stamping. The main reason is that the ink on the surface of the printed product is not dry or the post-processing of the UV on the surface of the printed product is improper, resulting in the poor combination of the ink and UV oil on the surface of the printed product and the surface of the paper. Solution: bronzing after printing is dry. In addition, anodized aluminum with low separation force and excellent heat transfer can be selected.

3. Discoloration of anodized aluminum after paste and hot stamping

The paste version is mainly caused by the bad production of the bronzing version, the galvanized aluminum is loosely installed, or the galvanized aluminum is not properly foiled. The discoloration of anodized aluminum after hot stamping is mainly caused by the high temperature of hot stamping. In addition, the wrinkling of anodized aluminum is also easy to cause uneven coloring of hot stamping and discoloration, which can be solved by appropriately lowering the temperature. For the round flattening model, a fan can be added at the foil feeding place to keep the foil pulling and flutter, to avoid the anodized aluminum touching the bronzing version and burning it before hot stamping.

4. Improper technological arrangement destroys the glossiness of the surface of the anodized aluminum, and the outline of the picture and text becomes fuzzy.

For hot stamping that requires film processing, people often worry that the gold foil is easy to wipe off and then hot stamping and then filming, which is easy to cause: â‘ The film (especially matte film) will destroy the gloss of the surface of the anodized aluminum, and it is not suitable to use water-soluble glue film Otherwise, it will cause blackening of the surface of the anodized aluminum, and at the same time it is very easy to cause the gold powder to stick to the edges of the graphics and cause virtual phenomenon. â‘¡After bronzing, it will sag due to pressure, and the glue is not easy to penetrate the surface of the anodized aluminum, which may cause the separation of OPP and paper at the bronzing place and affect the quality of the product. The correct process is to cover the film before bronzing, and choose the anodized aluminum that matches OPP.

In short, there are many factors that affect the quality of bronzing. Making a high-quality bronzing version and correctly mastering the suitability of bronzing are the key to improving the quality of bronzing.

9. Transformation of bronzing process

In the application of bronzing process, it will encounter the problem of how to improve work efficiency in production, especially the process improvement of large quantities of products is very necessary. For example, in the case of the printing of the "Red Three Rings" clamshell cigarette label, the original production process requires offset stamping and oiling. After changing to a new material, offset printing and oiling can be done once and then bronzing. Reduce one process in offset printing to avoid paper die-cutting and color explosion (reducing the impact of ultraviolet irradiation once), without affecting the normal progress of the bronzing process, greatly improve production efficiency, reduce scrap rate, and reduce Adverse effects on the production of other products.

Direct bronzing on the surface of UV varnish, the process itself has very high requirements for UV varnish and bronzing anodized aluminum. When applying varnish, pay attention to control the amount of oil, try to ensure that the relative varnish coating of the entire batch of products Stable, and the oil layer should be thin and flat; for the anodized aluminum used for bronzing, it is required to achieve high temperature resistance, good adhesion, and good bronzing adaptability with varnish (resin used in varnish The type matches the hot-melt adhesive in bronzing anodized aluminum). In all products, this process has a smaller range of application. In addition, the anodizing of aluminum on gold, silver ink and dumb oil also electrifies the bronzing surface and bronzing Aluminum has very high requirements. If the ink particles on the gold foil surface are large or the surface is rough, it will directly affect the normal progress of the gold foil.

10. Matters needing attention in hot stamping process:

(1). Must choose suitable hot stamping foil according to different varieties of hot objects. When hot stamping, it is necessary to master the three-way cooperation of temperature, pressure and hot stamping speed, and it will be different according to different hot stamping materials and hot stamping area.

(2). When cutting, you should master the speed and direction of the turning tool;

(3). Anodized aluminum hot stamping foil should use paper, ink (especially black ink), kerosene, compound glue with suitable properties. The hot stamping parts must be kept dry to avoid oxidation or damage to the bronzing layer;

(4). The general packaging is: 0,64 Ã— 120m one roll, one box per 10 rolls: customizable width is 0.64m, length is 240m or 360m large roll or other special specifications;

(5). Store it in a cool and ventilated place against pressure, moisture, heat and sun.

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